Each and every story is composed of the same five basic elements: a (1) hero who finds himself stuck in a (2) situation from which he wants to free himself by achieving a (3) goal. However, there is a (4) villain who wants to stop him from this, and if he’s successful, will cause the hero to experience a (5) disaster.
I know many writers struggle with summarizing their fiction in an appealing way.
The above method may help.
If you don't have those five elements in your novel, think about why that's so. Maybe it's time to do a little revision.